Drywall has become a dominant material in the production of interior building partitions. In particular, interior building partitions generally comprise a vertical stud wall which is used as a support for preformed drywall panels that are attached to the stud wall. Joints between adjacent panels of drywall are usually taped, and finished with joint or drywall compound. One type of apparatus or tool for applying joint compound is disclosed in U.S. Pat. No. 2,815,142 issued Dec. 3, 1957. This apparatus mechanically applies tape and joint compound contemporaneously. The apparatus includes a reservoir for joint compound which needs to be filled before applying the joint compound to the drywall surface. After the tape and the first coat of joint compound has been applied over the joint, it is typical to apply a second and sometimes even a third coat of joint compound. The second and third coats are typically applied using finishing tools such as a corner head, or a flat box.
A pneumatic apparatus for applying joint compound is disclosed in Denkins et al. U.S. Pat. No. 5,863,146 issued Jan. 26, 1999. This apparatus also needs to be filled with joint compound before applying the joint compound to the joint between adjacent panels of drywall. The apparatus is powered by compressed air which can be metered to control the application of joint compound. Several finishing attachments, such as disclosed in co-pending U.S. patent application Ser. No. 10/610,459 filed Jun. 30, 2003, can be attached to the apparatus.
When using pneumatic apparatus of the type described above, a substantial amount of time can be spent filling application tools with drywall compound. Each time a storage body on the tool needs to be filled, the drywall taping and finishing operations are interrupted which cause delays in the overall production of the building partitions. Prior art storage bodies are sized to hold an ample amount of drywall compound which significantly adds to the weight of the tool borne by an operator. In addition, when working with pressurized compressible drywall compound, issues arise in controlling certain aspects of the drywall compound flow. For example, problems have existed in stopping the flow of the drywall compound which tends to ooze out of the tool sometimes for 30 seconds after the air pressure has been cut off. This operating defect results in a wasted, messy discharge which must be cleaned up by the operator. Further problems have been experienced in the responsiveness of starting the drywall compound flow from the tool.
It is therefore desirable that the apparatus for applying drywall compound to wallboard joints be provided with a unique design and control arrangement which will overcome the deficiencies of the prior art and enhance the operability, speed and efficiency in all aspects of drywall taping and finishing operations.